The molecular consequences resulting from alterations of the extracellular ionic environment as they relate to the translation process in virus infected and uninfected eukaryotic cells are being investigated. Treatment of cultured animal cells with growth medium made hypertonic by the addition of excess NaCl results in a selective and reversible inhibition of polypeptide chain initiation. Furthermore, exposure of virus infected cells to hypertonic growth medium results in a preferential inhibition of host protein synthesis. An attempt to localize the initiation event inhibited by hypertonic treatment has been made by a) examining the effect of hypertonic treatment on the binding of met-tRNAf to 40S ribosomal subunits in intact cells exposed to excess NaCl and by b) measuring the ability of other inhibitors of polypeptide chain initiation to prevent the recovery of protein synthesis after hypertonic treated cells are returned to isotonic conditions. The combined results suggest that hypertonic treatment inhibits at a step following met-tRNAf binding to the 40S subunit and prior to the joining of the 40S-met-tRNAf-mRNA complex to the 60S subunit. Results from current studies aimed at developing a permeabilized cell system active in protein synthesis suggests that such a system will be a useful tool for understanding the molecular basis of hypertonic-treatment mediated inhibition of protein synthesis and mechanisms of translational control in general.